librbcodec

I realize I all but disappeared last summer when GSoC ended, and I'm sorry for
leaving my work unfinished. I've spent some more time on it, and completed the
patches that create librbcodec[0].

I think it's a reasonable way of separating the DSP, metadata, and codec code
so they can be used by other software, but I haven't gotten much feedback on my
overall approach. Does my code have the potential to be committed?